Casting of metal ingots



l n 5 i 5 v l K. E. MANN CASTING OF METAL INGOTS Filed April 8, 1964 Aug. 30, 1966 m H 2 Il Ilt|\| SOLI DIFICATION INVENTOR KAR/ Efe/V57' MAN/v *D r 47444 MLV AToRN Ys United States Patent O 3,268,963 CASTING F METAL INGOTS Karl Ernst Mann, Meinerzhagen, Westphalia, Germany, assignor to Otto Fuchs KG., Westphalia, Germany, a corporation of Germany Filed Apr. S, 1964, Ser. No. 358,303 Claims. (Cl. 22-212) The invention relates to the casting of metal ingots, especially of light weight metals and their alloys, by tincan casting.

The tin-can casting process developed to industrial maturity about 25 years ago has been described in Swiss Patent 221,650. A Beck and K. E. Mann have reported on its historical development, its theoretical bases and its practice in an article in the publication Aluminiumj vol. 29, (1953). Apparently there has been no further development beyond the state of the art described in that article, and, alongside the highly developed continuous casting processes, the tin-can casting process has been unable to achieve any industrial significance to date, in spite of the good results it has achieved.

In this process, the molten metal that is to be cast into ingots is placed in a thin-walled mold--the so-called tin can-whose wall thickness expediently amounts to from 1/100 to 1/{30 of the diameter of the ingot to be produced, and, by a relative movement between a coolant bath and the mold, it is gradually solidied from the bottom up, the metal in the mold above the surface of the coolant being kept in the fully molten state by heating means surrounding the mold. The mold is either lowered gradually from a furnace into the coolant bath on a descending support, or the level of the coolant bath is gradually raised relatively to the stationary mold. In the first case, the furnace remains stationary while the mold moves downward, and in the second case it is elevated as the coolant level rises.

The mounting of the heating units (which can expediently be of an electrical nature) in a heating muflie, and the raising and lowering of the furnace is complicated. Preferably, the raising and lowering of the furnace was to be performed independently of the raising and lowering of the mold, so that two separate hydraulic systems were needed.

An object of the invention is the casting of ingots, especially of light metals and light-metal alloys, by tincan casting, characterized in that no relative movement takes place between the heating units and the mold (tin can T)his and further objects of the invention will be apparent from the following description in conjunction with the drawings in which FIG. 1 is a schematic perspective view, partly in section, showing an embodiment of the invention; and

FIG. 2 is a schematic perspective View partly in section showing a flanged cover arrangement.

The heating units of a device in accordance with the invention must be so constructed that an adequate removal of heat from the mold through the units is possible, and the cooling chamber must be adequately constructed big enough to receive so much cooling water that a discoidal solidication of the metal is guaranteed in spite of the heating which continues during the soliditication. It is indeed -possible to perform the casting in such a manner that the mold is introduced into the coolant bath gradually, together with the heating Iunits. It is more advantageous, however, gradually to raise the level of the coolant bath while the mold and the heating units remain stationary, because in such a method of procedure it is possible entirely to eliminate the apparatus for raising and lowering the mold and the heating units.

ICC

The mold stands with the heating units surrounding it on a base which is placed in the coolant tank. The solidilication of the metal is brought about by elevating the icoolant level by means of the controlled feeding of coolant.

To protect the melt that is to be solidified from the influence of vaporized coolants, such as water vapor or humidity, the mold is expediently sealed airtight with a lid, as for example shown in FIG. 2, since otherwise an undesirable absorption of gas into the melt could take place.

In the preferred embodiment of the invention, in which the coolant level is raised during the solidiiication -process, the mold can be lilled after it has .been placed empty on its base in the coolant tank. Then, if desired, a seco nd degassing of the melt can be performed, by chlorinat1on for example, before the solidification process is begun.

Heat can be supplied to the molten metal above the solidification zone by electrical heating means, namely by resistance heating or by electroinductive heating. In this case it is possible to divide the electrical heating units into sections and, in the course of the solidi-cation process, to shut off those sections which are beneath the coolant level.

As more fully described in my copending application Ster. No. 358,047, filed April 7, 1964, if electrical induction heating is used, it is possible to exercise a stirring effect on the melt, thus promoting the formation of crystallization nuclei above the solidification zone. The intensity of the stirring can be controlled as desired by combining electrical induction heating with resistance heating.

A very intense stirring action brought about by the use of electroinductive heating means also makes it possible to achieve a uniform and line distribution in the melt of those alloy components which are diicultly soluble or insoluble therein at the casting temperature, as for example in the casting of aluminum alloys containing substantial amounts of lead, cadmium, bismuth and tin.

The quality of the ingots produced by the process of the invention can be improved by extensively preventing the formation of gas voids in the ingot; this is achieved by l creating a vacuum in the space above the surface of the metal in the mold during the progressive solidication of the metal, or by filling the said space with an inert gas, such as argon, under pressure. In the system known in the art, in which the mold is in a narrow heating muffle which is closed at the top and out of which it is lowered, the creation of a vacuum or overpressure presents difficulties. The mold must be sealed vacuum-tight or pressure-tight as the case may be; this means increasing the inside diameter of the heating Inutile, which results, however, in a loss of heating eciency. Also, the suction line or gas pressure line must be brought through a lid on the heating muffle in a flexible manner; the drilling of the muifle, which is thus made necessary, further reduces the heating eiciency of the mutile, and, in this arrangement, a long, exible vacuum or pressure line is unavoidable. The stationary arrangement of the mold and of the heating units during the soldication process, as proposed by the inventor, results, in these procedures, in the special advantage that the vacuum or pressure lines to a lid flangemounted on the mold need to have but slight flexibility, and that the creation of a sealing ange of sufficient breadth on the upper margin of the mold presents no difficulties of any kind.

The process is described and explained further, by way of example, with the aid of the drawing.

FIG. 1 shows a mold and the associated heating units.

FIG. 2 shows a mold with sealed lid and a conduit leading to the lid.

In FIG. 1, a base 1, on which the mold 2 stands, is disposed on the bottom of a coolant tank which, for the sake of clarity, is broken away.

The electrical heating units 3 surrounding the mold consist of a massive copper band which is wound into a coil. To this copper coil are fastened leads 12, connectable to a transformer (not shown) which is connected to the power line. Copper tubes can be used instead of a copper band, if cooling of the induction coil is necessary. If it is intended to provide only heating of the melt, without inductive stirring, this can be accomplished by a bilar winding of the coil, which cancels the magnetic field of a single coil.

The mold is filled with the metal or alloy to be cast, and then the melt is subjected, if desired, to a refining treatment. After the desired casting temperature has been established by means of the heating units, water is introduced into the coolant tank by a conventional inlet (not shown), the level is raised in the direction of the arrow by the controllable feeding of the water at the desired rate, and thus the molten metal in the mold is gradually brought to solidication from the bottom of the mold up. FIG. 1 shows the solidification process in the position in which the coolant level has been raised to the level 4 and the molten metal in the mold has solidified accordingly, to approximately the same level 5.

After completion of the solidication process the current is shut off and then the cooling water is let out. The mold is taken out of the heating units and the ingot is taken from the mold.

In FIG. 2, the mold 2' has a flange 6 on which a lid 7 is fastened air-tight with the interposition of a seal 8, by means, for example, of screws 9. A conduit 10 is welded into the lid, and is connected through a exible connecting line 11 to a conventional apparatus for the production of a vacuum or of an overpressure (not shown).

When using the heating coil as an inductive coil, or when providing an induction coil associated with the heating coil, helix of the inductive coil substantially corresponds to the induction coil set forth in my said copending application and is constructed and used as therein fully set forth.

I claim:

1. In the tin-can casting process of metals and their alloys in which the molten metal, placed in the tin can,

is gradually solidified from the bottom of the tin can up by a relative movement between a coolant bath and the tin can, while maintaining that metal amount in the tin can being above the level of the coolant in the fully molten state by heating means surrounding the tin can, the improvement which comprises that no relative movement takes place between said heating means and the tin can during the solidifying proceedings.

2. In the tin-can casting process of metals and their alloys in which the molten metal, placed in the tin can, is gradually solidified from the bottom of the tin can up by a relative movement between a coolant bath and the tin can, while maintaining that metal amount in the tin can being above the level of the coolant in the fully molten state by heating means surrounding the tin can, the improvement which comprises raising the level of the coolant while both the tin can and electric heating means surrounding the tin can in heat exchange relation therewith remain stationary during the solidifying proceedings, said heating means are at least one of the group of the resistance and electro-inductive heating means.

3. Improvement according to claim 2 in which the molten metal in the tin can is substantially maintained under vacuum.

4. Improvement according to claim 2 in which the molten metal in the tin can is substantially maintained under inert gas pressure.

5. Improvement according to'claim 2 in which the tin can is provided with hermetic closure means and gas conduit means into the space below said closure means.

References Cited by the Examiner UNITED STATES PATENTS 1,812,172 6/1931 Rohn 22-212 FOREIGN PATENTS 532,622 1/1941 Great Britain.

OTHER REFERENCES Magnesium Ingots, by Menzen, P. and Patterson- Rackwitz W., Metal Industry, September 7, 1945, page 151.

J. SPENCER OVERHOLSER, Primary Examiner.

V. K. RISING, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,268,963 August 30, 1966 Karl Ernst Mann It is hereby certified that error appears in the above numbered patentl requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, between lines 6 and 7, insert the following:

Claims priority, application Germany, Apr. 13, 1963, P39488 Signed and sealed this lst day of August 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN THE TIN-CAN CASTING PROCESS OF METALS AND THEIR ALLOYS IN WHICH THE MOLTEN METAL, PLACED IN THE TIN CAN, IS GRADUALLY SOLIDIFIED FROM THE BOTTOM OF THE TIN CAN UP BY A RELATIVE MOVEMENT BETWEEN A COOLANT BATH AND THE TIN CAN, WHILE MAINTAINING THAT METAL AMOUNT IN THE TIN CAN BEING ABOVE THE LEVEL OF THE COOLANT IN THE FULLY MOLTEN STATE BY HEATING MEANS SURROUNDING THE TIM CAN, THE IMPROVEMENT WHICH COMPRISES THAT NO RELATIVE MOVEMENT TAKES PLACE BETWEEN SAID HEATING MEANS AND THE TIN CAN DURING THE SOLIDIFYING PROCEEDINGS. 